Balance Sheet Components - Cash, Cash Equivalents and Short-Term and Long-Term Investments (Detail) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Cash	[1]	$ 985,382	$ 345,119
Money market funds		427,135	400,388
Certificate of deposit		0	2,969
Total cash and cash equivalents		1,412,517	748,476	$ 2,228,838
Total short-term and long-term investments		37,514	13,451
Total cash, cash equivalents and short-term and long-term investments		1,450,031	761,927
Certificates of deposit
Investment Holdings [Line Items]
Total short-term and long-term investments		31,351	6,988
Publicly traded equity securities
Investment Holdings [Line Items]
Total short-term and long-term investments		$ 6,163	$ 6,463

[1] Excludes restricted cash.